An absent-minded academic had just moved to a new house further along the same street. All too aware of his tendency to forget things, his wife took the precaution of writing down the new address on a piece of paper before he set off for work that morning.
“Here’s the key to our new house,” she said, “and remember, don’t come back here this evening, go to the new address.”
“Very well, dear,” he replied, and set off for work.
Inevitably in the course of the day he mislaid the slip of paper and, forgetting all about the move, he automatically returned to the old address. When he tried the key, he couldn’t get in. This prompted him to remember the move and to search in his pockets for the piece of paper, which was nowhere to be found.
In desperation, he wandered along the street and stopped the first approachable young man he came across.
“Excuse me, young man, I’m Professor Richardson. You wouldn’t happen to know where I live, would you?”
The boy sighed. “Come with me Dad,” he said.